Transmural ablation device with spring loaded jaws

ABSTRACT

A method and apparatus for transmural ablation using an instrument containing two electrodes or cryogenic probes. A clamping force is exerted on the two electrodes or probes such that the tissue of the hollow organ is clamped therebetween. Bipolar RF energy is then applied between the two electrodes, or the probes are cryogenically cooled, thus ablating the tissue therebetween. A monitoring device measures a suitable parameter, such as impedance or temperature, and indicates when the tissue between the electrodes has been fully ablated.

CROSS REFERENCE TO RELATED APPLICATION

This application is a division of application Ser. No. 10/038,506, filedNov. 9, 2001, which is a continuation-in-part of application Ser. No.10/032,378, filed Oct. 26, 2001, which is a continuation-in-part ofapplication Ser. No. 09/844,225, filed Apr. 27, 2001, now U.S. Pat. No.6,517,536, which is a continuation-in-part of application Ser. No.09/747,609, filed Dec. 22, 2000, now U.S. Pat. No. 6,546,935, whichclaims the benefit of provisional application Ser. No. 60/200,072, filedApr. 27, 2000.

BACKGROUND OF THE INVENTION

Atrial fibrillation is the most common heart arrhythmia in the world,affecting over 2.5 million people in the United States alone. Ablationof cardiac tissue, in order to create scar tissue that poses aninterruption in the path of the errant electrical impulses in the hearttissue, is a commonly performed procedure to treat cardiac arrhythmias.Such ablation may range from the ablation of a small area of hearttissue to a series of ablations forming a strategic placement ofincisions in both atria to stop the conduction and formation of errantimpulses.

Ablation has been achieved or suggested using a variety of techniques,such as freezing via cryogenic probe, heating via RF energy, surgicalcutting and other techniques. As used here, “ablation” means the removalor destruction of the function of a body part, such as cardiac tissue,regardless of the apparatus or process used to carry out the ablation.Also, as used herein, “transmural” means through the wall or thickness,such as through the wall or thickness of a hollow organ or vessel.

Ablation of cardiac tissue may be carried out in an open surgicalprocedure, where the breastbone is divided and the surgeon has directaccess to the heart, or through a minimally invasive route, such asbetween the ribs or via catheter that is introduced through a vein, andinto the heart.

Prior to any ablation, the heart typically is electronically mapped tolocate the point or points of tissue which are causing the arrhythmia.With minimally invasive procedures such as via a catheter, the catheteris directed to the aberrant tissue, and an electrode or cryogenic probeis placed in contact with the endocardial tissue. RF energy is deliveredfrom the electrode to the tissue to heat and ablate the tissue (or thetissue may be frozen by the cryogenic probe), thus eliminating thesource of the arrhythmia.

Common problems encountered in this procedure are difficulty inprecisely locating the aberrant tissue, and complications related to theablation of the tissue. Locating the area of tissue causing thearrhythmia often involves several hours of electrically “mapping” theinner surface of the heart using a variety of mapping catheters, andonce the aberrant tissue is located, it is often difficult to positionthe catheter and the associated electrode or probe so that it is incontact with the desired tissue.

The application of either RF energy or ultra-low temperature freezing tothe inside of the heart chamber also carries several risks anddifficulties. It is very difficult to determine how much of the catheterelectrode or cryogenic probe surface is in contact with the tissue sincecatheter electrodes and probes are cylindrical and the heart tissuecannot be visualized clearly with existing fluoroscopic technology.Further, because of the cylindrical shape, some of the exposed electrodeor probe area will almost always be in contact with blood circulating inthe heart, giving rise to a risk of clot formation.

Clot formation is almost always associated with RF energy or cryogenicdelivery inside the heart because it is difficult to prevent the bloodfrom being exposed to the electrode or probe surface. Some of the RFcurrent flows through the blood between the electrode and the hearttissue and this blood is coagulated, or frozen when a cryogenic probe isused, possibly resulting in clot formation. When RF energy is applied,the temperature of the electrode is typically monitored so as to notexceed a preset level, but temperatures necessary to achieve tissueablation almost always result in blood coagulum forming on theelectrode.

Overheating or overcooling of tissue is also a major complication,because the temperature monitoring only gives the temperature of theelectrode or probe, which is, respectively, being cooled or warmed onthe outside by blood flow. The actual temperature of the tissue beingablated by the electrode or probe is usually considerably higher orlower than the electrode or probe temperature, and this can result inoverheating, or even charring, of the tissue in the case of an RFelectrode, or freezing of too much tissue by a cryogenic probe.Overheated or charred tissue can act as a locus for thrombus and clotformation, and over freezing can destroy more tissue than necessary.

It is also very difficult to achieve ablation of tissue deep within theheart wall. A recent study reported that to achieve a depth of ablationof 5 mm, it was necessary to ablate an area almost 8 mm wide in theendocardium. See, “Mechanism, Localization, and Cure of AtrialArrhythmias Occurring After a New Intraoperative EndocardialRadiofrequency Ablation Procedure for Atrial Fibrillation,” Thomas, etal., J. Am. Coll. Cardiology, Vol. 35, No. 2, 2000. As the depth ofpenetration increases, the time, power, and temperature requirementsincrease, thus increasing the risk of thrombus formation.

In certain applications, it is desired to obtain a continuous line ofablated tissue in the endocardium. Using a discrete or point electrodeor probe, the catheter must be “dragged” from point to point to create aline, and frequently the line is not continuous. Multielectrodecatheters have been developed which can be left in place, but continuitycan still be difficult to achieve, and the lesions created can be quitewide.

Because of the risks of char and thrombus formation, RF energy, or anyform of endocardial ablation, is rarely used on the left side of theheart, where a clot could cause a serious problem (e.g., stroke) .Because of the physiology of the heart, it is also difficult to accesscertain areas of the left atrium via an endocardial, catheter-basedapproach.

Recently, epicardial ablation devices have been developed which apply RFenergy to the outer wall of the heart to ablate tissue. These devices donot have the same risks concerning thrombus formation. However, it isstill difficult to create long, continuous lesions, and it is difficultto achieve good depth of penetration without creating a large area ofablated tissue.

As noted above, other forms of energy have been used in ablationprocedures, including ultrasound, cryogenic ablation, and microwavetechnology. When used from an endocardial approach, the limitations ofall energy-based ablation technologies to date are the difficulty inachieving continuous transmural lesions, and minimizing unnecessarydamage to endocardial tissue. Ultrasonic and RF energy endocardialballoon technology has been developed to create circumferential lesionsaround the individual pulmonary veins. See e.g., U.S. Pat. No. 6,024,740to Lesh et al. and U.S. Pat. Nos. 5,938,660 and 5,814,028 to Swartz etal. However, this technology creates rather wide (greater than 5 mm)lesions which could lead to stenosis (narrowing) of the pulmonary veins.See, “Pulmonary Vein Stenosis after Catheter Ablation of AtrialFibrillation,” Robbins, et al., Circulation, Vol. 98, pages 1769-1775,1998. The large lesion area can also act as a locus point for thrombusformation. Additionally, there is no feedback to determine when fulltransmural ablation has been achieved. Cryogenic ablation has beenattempted both endocardially and epicardially (see e.g., U.S. Pat. No.5,733,280 to Avitall, U.S. Pat. No. 5,147,355 to Friedman et al., andU.S. Pat. No. 5,423,807 to Milder, and WO 98/17187, the latterdisclosing an angled cryogenic probe, one arm of which is inserted intothe interior of the heart through an opening in the heart wall that ishemostatically sealed around the arm by means of a suture or staples),but because of the time required to freeze tissue, and the deliverysystems used, it is difficult to create a continuous line, and uniformtransmurality is difficult to verify.

Published PCT applications WO 99/56644 and WO 99/56648 disclose anendocardial ablation catheter with a reference plate located on theepicardium to act as an indifferent electrode or backplate that ismaintained at the reference level of the generator. Current flows eitherbetween the electrodes located on the catheter, or between theelectrodes and the reference plate. It is important to note that thisreference plate is essentially a monopolar reference pad. Consequently,there is no energy delivered at the backplate/tissue interface intendedto ablate tissue. Instead, the energy is delivered at theelectrode/tissue interface within the endocardium, and travels throughthe heart tissue either to another endocardial electrode, or to thebackplate. Tissue ablation proceeds from the electrodes in contact withthe endocardium outward to the epicardium. Other references discloseepicardial multielectrode devices that deliver either monopolar orbipolar energy to the outside surface of the heart.

It is important to note that all endocardial ablation devices thatattempt to ablate tissue through the full thickness of the cardiac wallhave a risk associated with damaging structures within or on the outersurface of the cardiac wall. As an example, if a catheter is deliveringenergy from the inside of the atrium to the outside, and a coronaryartery, the esophagus, or other critical structure is in contact withthe atrial wall, the structure can be damaged by the transfer of energyfrom within the heart to the structure. The coronary arteries,esophagus, aorta, pulmonary veins, and pulmonary artery are allstructures that are in contact with the outer wall of the atrium, andcould be damaged by energy transmitted through the atrial wall.

Accordingly, it is the object of the present invention to provide animproved method and device for making transmural ablations to hearttissue.

It is a related object to provide a method and device for makingtransmural ablation in heart tissue that minimizes unnecessary damage tothe heart tissue.

It is a further object to provide a method and device for makingtransmural ablation in heart tissue that creates continuous lesions in asingle step.

SUMMARY OF THE INVENTION

These objects, and others which will become apparent upon reference tothe following detailed description and attached drawings, are achievedby the use of a clamping and ablating device for use in treating cardiacarrhythmia having first and second handle members, with first and secondmating jaw members associated with the first and second handle members.The jaw members are movable between a first open position and a secondclamped position. The jaw members have outer surfaces with opposedmating surfaces. Each mating surface has a central region, with thecentral region of the first jaw being aligned with the central region ofthe second jaw. A first elongated electrode extends along the centralregion of the first jaw and a second elongated electrode extends alongthe central region of the second jaw. The first and second electrodesare adapted to be connected to an RF energy source so that, whenactivated, the electrodes are of opposite polarity. At least one of thejaw members is biased by a spring so as to urge the jaw members towardthe clamped position with a force that increases as the separation ofthe jaws increases.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view showing a procedure in accordance with thepresent invention utilizing ablation elements operatively connected toeither a source of RF energy or cryogenic fluid.

FIG. 2 is a cross-section of an ablation element for use in the presentinvention taken along lines 2—2 of FIG. 1.

FIGS. 3-6 show alternate configurations for the ablation elements ofFIG. 2.

FIG. 7 shows a further step in the inventive procedure in which tissueis clamped between the ablation elements.

FIGS. 8-12 schematically illustrate the inventive procedure so as tomake a transmural lesion that fully circumscribes a pulmonary vein, withFIG. 9 showing a cross-sectional view of the clamp/ablation element incontact with the atrial tissue to express blood from the clamped area.

FIGS. 13-17 show a further method according to the present invention inwhich transmural lesions are made so as to circumscribe both pulmonaryveins.

FIGS. 18-22 show a further procedure in which a transmural lesion ismade so as to circumscribe a single pulmonary vein.

FIGS. 23-27 illustrate a further procedure in which a transmural lesionis made so as to circumscribe both pulmonary veins.

FIG. 28 is a perspective view of a further embodiment of a grasper foruse in an open chest procedure in accordance with the present inventionshowing the grasper in its “closed” position.

FIG. 29 is a perspective view of the grasper of FIG. 28 with the grasperin its “open” position.

FIG. 30 is an enlarged perspective view of the working position of thegrasper of FIG. 28 with the grasper jaws in the “closed” position.

FIG. 31 is an enlarged perspective view of the working portion of thegrasper of FIG. 28 with the grasper jaws in the “open” position.

FIG. 32 is an enlarged cross-sectional view of the grasper jaws for thegrasper of FIG. 28.

FIG. 33 is a perspective view of a further embodiment of a grasper,which may be used in either an open or a minimally invasive procedure,along with its associated electrosurgical generator.

FIG. 34 is a side view of the grasper of FIG. 33 showing the grasper inits “open” position.

FIG. 35 is an exploded perspective view of the grasper of FIG. 33.

FIG. 36 is a side cross-sectional view of the grasper of FIG. 33 withthe grasper jaws in the “open” position.

FIG. 37 is a side cross-sectional view of the grasper of FIG. 33 withthe grasper jaws in the “closed” position.

FIG. 38 is a cross-sectional view taken along line 38—38 of FIG. 34showing the grasper jaws in the “open” position.

FIG. 39 is a cross-sectional view of the grasper jaws taken along theline 39—39 of FIG. 37 showing the grasper jaws in the “closed” position.

FIG. 40 is a cross-sectional view of the graspers taken along line 40—40of FIG. 34.

FIGS. 41-51 show alternate constructions for the electrodes suitable foruse in the present invention, with FIGS. 41 and 43-51 beingcross-sectional views similar to FIGS. 38 and 39, and FIG. 42 being across-sectional view taken along line 42—42 of FIG. 41.

FIGS. 52A-K illustrate eleven different ablations to the left and rightatrium (as seen from behind in FIG. 52A) and the methods for making thelesions (FIGS. 52B-K).

FIG. 53A is a perspective view of a further embodiment of device forperforming transmural ablation according to the present invention.

FIG. 53B is a perspective view of the transmural ablation device of FIG.53A with a portion removed to show detail.

FIG. 54 is an exploded perspective view of the transmural ablationdevice of FIG. 52.

FIG. 55 is a longitudinal cross-sectional view of an obturator tipelectrode for use in the device of FIG. 52.

FIG. 56 is a piercing tip electrode for use in the device of FIG. 52.

FIG. 57 is an enlarged side view of the tip of the instrument shown inFIG. 52.

FIGS. 58A-58G illustrate the use of the instrument of FIG. 52 to form atransmural ablation.

FIG. 59 shows a series of transmural ablations contemplated by the MAZEprocedure.

FIGS. 60A-60I illustrate a procedure for performing a circumferentiallesion in lumen such as a pulmonary vein.

FIGS. 61A-61J show the use of the instrument of FIG. 52 for forming acontinuous transmural ablation around a pair of pulmonary veins.

FIGS. 62A-I show a further device for performing transmural ablationsand the method for making such ablations.

FIG. 63 is a perspective view of a further embodiment of a grasperadapted for use in minimally invasive procedures.

FIG. 64 is an enlarged plan view of the handle position of the grasperof FIG. 63, with portions removed to show detail.

FIGS. 65A and 65B are enlarged plan views of the jaw actuation mechanismfor the grasper of FIG. 63.

FIG. 66 is an enlarged fragmentary perspective view of the jaws ofgrasper of FIGS. 33-40.

FIG. 67 is an enlarged perspective view of the tip of the fixed jawshown in FIG. 66.

FIG. 68 shows an anterior plan view of the heart in the chest cavity andan access location for performing ablation where the chest cavity isopened.

FIG. 69 shows an anterior plan view of the heart with an opening in thechest cavity.

FIG. 70 shows a side view of a bullet dissector according to the presentinvention.

FIG. 71 shows an enlarged side view of the bullet dissector.

FIG. 72 shows an enlarged side view of the opened chest cavity includinga bullet dissector.

FIG. 73 shows an anterior plan view of the chest cavity showing ablationaccording to the open heart method.

FIG. 74 illustrates ablations to the right and left atrium as seen frombehind.

FIGS. 75-76 illustrates bilateral ablation of the left atrium near theright and left pulmonary veins.

FIG. 77 illustrates a schematic diagram of the heart with ablationsaccording to the methods of the present invention.

FIG. 78 is an anterior plan view of the heart and access locations forperforming ablation according to the intercostal method.

FIG. 79 is a top perspective view of the patient showing intercostalinsertion of the bullet dissector into the chest cavity.

FIG. 80 is an anterior plan view of the heart showing intercostalinsertion of the bullet dissector into the intrapericardial space.

FIG. 81 is a sectional view along plane 81—81 of FIG. 80.

FIG. 82 is a sectional view, similar to FIG. 81, showing insufflation ofthe bullet dissector.

FIG. 83 is a sectional view, similar to FIG. 81, showing insertion of anablation device.

FIG. 83A is a plan view of a cardiac grasper similar to the graspershown in FIGS. 33-37 with right curved jaw members.

FIG. 83B is a plan view of a cardiac grasper similar to the graspershown in FIGS. 33-37 with left curved jaw members.

FIG. 84 is a sectional view along plan 84—84 of FIG. 83 with portions ofthe patient's body removed.

FIGS. 85-86 are sectional views, similar to FIG. 81, showing intercostalablation being performed with the lungs inflated.

FIG. 87 is an anterior plan view of the heart and access locations forperforming ablation according to the sub-xyphoid method.

FIG. 88 is an anterior plan view of the heart showing insertion of thebullet dissector and ablation device according to the sub-xyphoidmethod.

FIG. 89 is an enlarged side view of the heart showing an ablation deviceinserted according to the sub-xyphoid method.

FIG. 90 is an enlarged side view of the heart showing ablation accordingto the sub-xyphoid method.

FIG. 91 is an anterior plan view of the heart showing ablation of theright and left pulmonary veins according to the sub-xyphoid method.

FIG. 92 is an anterior plan view of the heart showing an alternateinstrument inserted according to the sub-xyphoid method.

FIG. 93 is an enlarged side view of the heart showing ablation using thealternate instrument.

FIG. 94 is a top plan view of the alternate instrument.

FIG. 95 is a side view of the heart and alternate instrument showingablation according to the intercostal method.

FIG. 96 shows an anterior plan view of the heart and access location forperforming ablation according to the sub-xyphoid method using a singlesub-xyphoid access location.

FIG. 97 shows an anterior plan view of the heart during insertion of thebullet dissector through the sub-xyphoid access location.

FIGS. 98-99 show an enlarged side view of the heart illustratinginsertion of the bullet dissector into the intrapericardial space anddissection by the bullet dissector around the left pulmonary veins.

FIG. 100 shows an anterior plan view of the heart similar to FIG. 97further including insertion of the ablation device.

FIG. 101 shows an enlarged side view of the heart illustrating ablationwhere sub-xyphoid access of the bullet dissector and ablation device isachieved using a single sub-xyphoid access location.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

With reference to the present invention, the compression of the atrialtissue is important because it insures that the exposed electrodesurface or cryogenic probe is not in contact with any tissue or bloodexcept the clamped tissue to be ablated. Specifically, the clamping ofthe tissue between the electrodes or cryogenic probes insures that theconductive or cooled area is only in contact with the clamped tissue.The compressed tissue acts to isolate the electrically active orcryogenically cooled surface, and prevents inadvertent energy deliveryto other parts of the heart or blood. The outside temperature of theelectrode can easily be monitored to insure that the temperature of theinsulation in contact with blood remains below a critical temperature(40° C., for example).

In one form of the invention, transmural ablation using RF energy isaccomplished by providing an atrial ablation device having a lower “j”clamp/electrode element and placing it on the atrial tissue below thepulmonary veins.

Once the pulmonary veins have been isolated, an upper clamp/electrodeelement is introduced, and the clamp assembly “J” is worked back ontothe epicardial atrial tissue. Once the jaws are positioned below theostia of the pulmonary veins, the tissue is partially clamped, allowingcontinued flow from the pulmonary veins to the left atrium. Once theclamps are safely away from the pulmonary vein tissue, and onto atrialtissue, the clamps are closed together to compress the tissue. Once thetissue is compressed, bipolar RF energy is used to ablate the clampedatrial tissue. The clamps are then removed, the lesion having beencreated. Lesions may also be created by inserting one clamp/electrodeelement through an incision in the heart so as to permit contact withendocardial tissue. This incision may be created with a separateinstrument. Alternatively, the tip of one of the jaws may have apiercing structure associated therewith for making the entry incision.Once the clamps are properly located, the tissue is compressed and RFenergy is applied.

Turning now to the figures of the drawings, a method embodying thepresent invention is shown schematically in FIG. 1. A clamping typedevice 10 is provided to group the two walls 22, 24 of the atrium 20,and delivers bipolar RF energy through both walls held between the twoupper and lower clamp jaws 50, 51. FIG. 1 shows the upper and lowerparallel clamp jaws 50, 51 and electrodes 52, 53 positioned above andbelow atrial tissue 22, 24, distal to the pulmonary veins. FIG. 2,Section 2—2 of FIG. 1, shows a cross-section of the clamping memberincluding the insulator 28 and electrode 53. Alternate configurations ofthe clamping members are shown in FIGS. 3-6. FIG. 3 shows a crosssection of the electrode consisting of an insulating layer 11, and aconductive strip 12. The electrode of FIG. 3 may be constructed of atungsten wire as the conductive material 12, with polyamide as theinsulating material 11. The conductive strip is created by exposing apart of the tungsten wire through the polyamide.

FIGS. 4 and 5 show an alternate electrode construction consisting of acarbon fiber element 13, and an insulating material 14, such as ABS. Theconductive strip 15 may be comprised of a copper/gold electrode platedonto the ABS. FIG. 6 shows a cross section of yet another possibleelectrode design where the conductive material 16 consists of astainless steel needle with lumen 17 and insulating material 18.

FIG. 7 shows the parallel jaws 50, 51 clamping and ablating the atrialtissue 20 distal to the pulmonary veins 26. Proximal point A is clampingand ablating the atrial tissue distal to the pulmonary veins. Proximalpoint A is the most proximal point of ablated tissue on both the upperand lower atrial wall. Distal point B is the most distal point ofablated tissue on both the upper and lower atrial wall.

FIGS. 8-12 show the inventive procedure that fully circumscribes apulmonary vein with transmural lesions. FIG. 8 shows a top view of theinstrument jaws positioned for a 2-step isolation of a single pulmonaryvein. The lower jaw is directly beneath the upper jaw, and is not shown.Proximal point A and distal point B correspond to FIG. 7.

FIG. 9 shows a cross-sectional view of the jaws clamping and ablatingatrial tissue. Importantly, FIG. 9 shows that the electrode/clampconfiguration provides a clamped zone of tissue that is wider than thezone of ablated tissue. This is achieved by using an electrode widththat is narrower than the clamped tissue width, and preferably less thanone-third of the clamped tissue width. As shown in FIG. 9 (and betterillustrated in FIG. 26), the electrode forms the apex of the triangularclamping member. Other convex shapes are also contemplated.

The wider zone of clamped tissue serves several purposes. When theclamping members are closed onto tissue, any blood in the clamped zoneis squeezed or expressed out. Further, the distance between theelectrodes is minimized, so that the ablation zone remains narrow. It isimportant to isolate the blood from the ablation zone to avoid creatingthrombus. Accordingly, a clamped zone that isolates the ablation zonefrom the blood minimizes the temperature at the periphery of theablation zone and will reduce the likelihood of the formation ofthrombus by the blood in contact with the clamped zone.

Once tissue has been fully ablated with the clamp in the position shownin FIG. 8, an ablation line of tissue on both upper and lower atrialwalls is created. This is shown as ablation line 60 in FIG. 10. Theclamp is then repositioned to the position shown in FIG. 10, so that thedistal point D overlaps the ablation line 60. The tissue is clamped andablated as shown in FIGS. 7 and 9, and a second ablation line 61 (FIG.11) is formed on both the upper and lower atrial walls. Proximal point Cand distal point D correspond to points A and B respectively. The fullablation line is shown in FIGS. 11 and 12 with points A-D as shown.

This “clamping” method and device for creating transmural lesions has anumber of advantages. First, using a two step method as shown allows forclamping and ablation of atrial tissue without stopping the blood flowfrom the pulmonary vein. Secondly, by clamping both walls together, anddelivering energy through the clamped tissue, the atrial tissue is notpenetrated. Because the atrial tissue is not penetrated, a larger jawcan be used, and the clamping force can be much higher because of theincreased stiffness of the jaw. Also, there is no concern of bleedingfrom an atrial puncture.

Another advantage of this method and device is that ablation of tissuewithin the pulmonary veins is avoided, as recent articles have shownthat ablation of tissue within the pulmonary veins can cause pulmonaryhypertension and stenosis. Specifically referring to FIGS. 13-17, alonger jaw could be used to create an ablation line through atrialtissue which electrically isolates both pulmonary veins using the samemethod.

FIGS. 18-22 show the clamping device in a curved-jaw embodiment thatcreates a circumferential lesion around the pulmonary vein in one step.FIGS. 18 and 19 show the clamp jaws positioned around the pulmonaryvein. FIGS. 20 and 21 show the device clamping and ablating atrialtissue distal to the pulmonary vein. FIG. 22 shows the resultingablation line 60.

FIGS. 23-27 show the same concept applied to a device and method forcreating a lesion around both pulmonary veins. The advantage of thisconcept is that the entire lesion is created in one step. Thedisadvantage is that blood flow from the pulmonary vein(s) is cut offduring ablation. Using a curved electrode also allows the user to ablatetissue more distal to the pulmonary vein than would be possible with astraight electrode. Note that this curved type electrode could be usedwith a two step procedure as described above, using “left” and “right”curved devices to create a lesion which was more distal to the pulmonaryveins. Note also that this method and device are not limited to usearound the pulmonary veins, but could be used anywhere in the atriumthat the clamp could be applied.

Turning to FIGS. 28-32, there is seen a further version of a cardiacgrasper 70 suitable for an open chest procedure in accordance with thepresent invention. The grasper 70 includes two ring handles 72, 74joined together for relative movement by a pivot screw or pin 76. Eachhandle 72, 74 has a jaw member 78, 80 respectively associated therewith,each jaw being curved so that it has a major portion that issubstantially perpendicular to the handles. This gives the grasper 70 anL-shaped appearance, with a working portion of the jaws being betweenapproximately 3-8 cm in length.

The grasper is made of a rigid material, such as stainless steel, and issubstantially encased in a durable insulating material, such as ABSplastic. With reference to FIG. 32, which shows the opposed jaw membersin cross section, the stainless steel structural support is designated82. The structural support 82 is completely encased by insulatingmembers 84, 86 and 88. The tips 78 a, 80 a of the jaws may be made of asoft, atraumatic material in order to reduce the likelihood ofunintentional injury of tissue by the jaws.

In keeping with the invention, the grasper jaws have raised or convex,opposed tissue clamping surfaces, 90, 92, respectively, with eachclamping surface, 90, 92 centrally supporting an electrode 94, 96,respectively, of opposite polarity. The spacing between the jaws issubstantially uniform or constant when in the closed or clampedposition. RF energy of opposite polarity is supplied to the electrodes94, 96 through conductors 98, 100, which are connected to an RFgenerator. As with the previously-described jaw members, thiselectrode/clamp configuration provides a clamped zone of tissue that issignificantly wider than the zone of ablated tissue created by theopposed electrodes. This causes for any blood in the clamp zone to besqueezed or expressed out of the ablation zone, thus reducing thelikelihood of thrombus formation, as well as minimizing the distancebetween the electrodes, so that the ablation zone remains narrow. Theclamping also eliminates the cooling effect of circulating blood.

With reference to FIG. 32, the electrodes 94, 96 have a T-shaped crosssection, with the cross portion of the T resting on the insulatingmember 88 and the upright portion of the T protruding through a narrowopening in the insulating member 84, thus creating an exposed electrodesurface that contacts the tissue grasped between the jaws. In practice,the electrodes are preferably made of gold-plated copper and extendalong substantially the entire working surface of the jaw members. Theexposed portions of the electrode are generally less than 1.25 mm inwidth, and preferably between approximately 0.12-0.6 mm in width. Thisinsures that most of the jaw surface is insulator, and that theelectrode comprises generally less than one-third of the width of thejaw.

In keeping with a further aspect of the invention, the graspers mayprovide feedback that permits the user to gauge the completeness (i.e.,degree of transmurality) of the ablation. Specifically, a transmurallesion blocks electrical signals because it is non-conductive scartissue. Because impedance is simply the inverse of conductivity, theability of the lesion to block electrical signals is accuratelyindicated by its impedance, which can be measured simultaneously withthe creation of the lesion. During RF energy application to the tissueto be ablated, the current and voltage applied to the tissue aremeasured, and the impedance calculated and stored. Based upon a functionof the impedance (e.g., its value, the change in value, or the rate ofchange in value) it is determined whether ablation is complete andtransmural. See e.g., U.S. Pat. No. 5,403,312, which is incorporated byreference herein. Indicator lights or other types of signals (e.g.,audible) may be associated with the grasper to correspond to the degreeof ablation determined by the impedance feedback system. For example,once the impedance reaches a certain level for a certain period of time,a red light may be activated to signal that ablation is complete.

In keeping with another aspect of the invention, a feedback system fordetermining the temperature of the ablated tissue is also provided. Tothis end, the jaws include a series of thermocouples 102 that aresupported in the insulating member 84 remote from the associatedelectrode 94 near the edge of the jaw 78. The thermocouples 102 protrudeslightly through the surface of the insulating member 84 so as to engageany tissue clamped between the jaws 72, 74. Wires 104 are attached tothe thermocouples 102 to transmit the information received to a remotelocation. Again, a visual or other indicator may be provided to alertthe user that a certain pre-determined critical temperature (e.g., 40°C.) has been reached, thus permitting the user to avoid undesiredthermal spread.

Turning to FIGS. 33-37, there is a further version of a cardiac grasper110 suitable for both open and minimally-invasive procedures inaccordance with the present invention. As seen in FIG. 33, the grasper110 includes a cord 112 for housing the conductors (not shown) and forplugging into an electrosurgical generator 114 to provide current to thegrasper 110. As discussed above, the generator 114 includes a display115 to provide a simultaneous visual indication of the degree ofconductance of the tissue being ablated. The instrument 110 includesopposed parallel, curved jaw assemblies 116, 118 with jaw assembly 116being fixed and jaw assembly 118 being movable between an open position(as seen in FIGS. 34 and 36) to a closed position (shown in FIG. 37),the spacing between the jaws being substantially uniform or constant.The fixed jaw assembly 116 comprises a fixed electrode 120, a fixedinsulator 122 and a fixed jaw cap 124. The fixed electrode 120 providesan electrical pathway adjacent to the tissue to be ablated and islocated on the inside of the fixed jaw assembly 116 (the “inside” beingdefined as the side that contacts the tissue to be ablated). The fixedinsulator 122 surrounds the fixed electrode 120 and forms the inside ofthe fixed jaw assembly 116. The fixed jaw cap 124 forms the backside ofthe fixed jaw assembly 116 (the “backside” being defined as the surfaceopposite the fixed electrode 120).

The drive jaw assembly 118 comprises a drive electrode 126, a driveinsulator 128, and a drive jaw cap 130. The drive electrode 126 providesa second electrical pathway adjacent the tissue to be ablated and islocated on the inside of the drive jaw assembly 118 (“inside” beingdefined as the side contacting the tissue to be ablated). The driveinsulator 128 surrounds the drive electrode 126 and forms the inside ofthe drive jaw assembly 118. The drive jaw cap 130 forms the backside ofthe drive jaw assembly 118 (“backside” being defined as the surfaceopposite the drive electrode 126) .

Each of the electrodes 120, 126 is attached to an electricallyconductive means, such as a wire, that runs the length of the extensionshaft and through the conductor cord 112 for coupling to the RFgenerator 114.

Each jaw assembly 116, 118 is supported by a two piece extension shaftcomprising a right fixed member 132 and left fixed member 134 (for thefixed jaw) and a right drive member 136 and left drive member 138 (forthe drive jaw 118). A shaft cap 139 covers the coextensive portions ofthe fixed members 132, 134 and the drive members 136, 138 (when the jawsare in the open position as seen in FIG. 34). The right fixed member 132and left fixed member 134 combine to form a structure that extends froma handle 140, through the shaft cap 139, and then terminating at thedistal end of the instrument 110 in the fixed jaw assembly 116 on theright and left sides, respectively, of the instrument. Similarly, theright drive member 136 and left drive member 138 extend from the handle140, through the shaft cap 139, and then terminate in the drive jawassembly 118 on the right and left sides, respectively, of theinstrument. The portions of the fixed members 132, 134 co-extensive withthe fixed jaw assembly 116 are joined by a fixed bridge 142 along thelength of the jaw. Similarly, the portions of the drive members 136, 138co-extensive with the drive jaw assembly 118 are joined together by adrive bridge 144 along the length the drive jaw 118.

The handle 140 comprises two mating halves 140 a, 140 b forencapsulating the actuation and force control mechanisms for thegrasper, as well as providing for grounding of the shaft components bymeans of a conductive shaft pin 141. In order to move the drive jawassembly 118 between its open and closed positions, the handle 140includes a lever comprising a pair of lever plates 146 and a levershroud 148. The lever is pivotally mounted on a support member 150extending between the two halves 140 a, 140 b of the handle 140, with alever spring 151 biasing the lever to its open position (FIG. 34). Thelever plates 146 are coupled by a lever pin 152 to a carriage 154 thatcaptures the proximal ends of the drive members 136, 138, so as toprovide translational motion to these members.

The carriage 154 includes a lost motion assembly comprising a carriagespring 156 for controlling the minimum and maximum loads that can beapplied to tissues that are to be captured between the jaw assemblies116, 118. As can be readily appreciated, the thicker the tissue that isgrasped between the jaws, the greater the compression of the spring 156,and the greater the compression force exerted by the jaws on the tissue.(The range of tissue thickness is expected to be between about 1-15 mm.)In other words, the force exerted by the jaws on the tissue heldtherebetween increases as the distance between the jaws increases.Adjustment of the compression force is accomplished by pre-loading thecarriage spring 156 with a load adjustment screw 158. The lost motionassembly also includes a thumb latch 160 for releasing the clampingpressure and for providing a mechanical stop for the spring-loadedcarriage 154. The thumb latch 160 is pivotally mounted on a latch pin162 to secure the thumb latch to the handle 140. Additionally, a latchspring 164 is provided for biasing the thumb latch 160 to its lockedposition. A latching step on the carriage 154 interfaces with the tip ofthe thumb latch 160 to provide for the mechanical stop.

When the lever is pivoted with respect to the handle 140, the drive jawassembly 118 and its drive members 136, 138 slide along the longitudinaldirection of the shaft to bring the two jaw assemblies 116, 118 intocontact with the tissue intended to be grasped.

In order to ablate a narrow, long region of biological tissue with theinstrument 110, the tissue is first placed between the open instrumentjaws 116, 118. The user then grasps the actuation lever comprising thelever plates 146 and lever shroud 148 to apply the force required todrive the drive members 136, 138 and drive jaw assembly 118 distally,thus compressing the tissue and automatically engaging the thumb latch160. The thumb latch 160 locks the position of the drive members 136,138 and the drive jaw assembly 118 with respect to the handle 140 andthe fixed jaw assembly 116. The amount of jaw force on the tissue iscontrolled by the lost motion assembly between the lever and the drivemembers 136, 138.

With the jaws closed on the tissue, the operator activates the RFgenerator 114. RF energy passes through the tissue between theelectrodes 120, 126, thus ablating the tissue between these electrodes.After completion of the ablation cycle, the operator releases theclamping of the tissue by depressing the thumb latch 160, thus releasingthe carriage 154. With the carriage 154 released, the lever spring 151drives the drive members 136, 138 and the drive jaw assembly 118proximally to their open positions. The actuation lever, since it isdirectly coupled to the carriage 154, also returns to the open position.

Turning to FIGS. 41-51 there is seen in schematic form variousconfigurations for the electrodes 120, 126 for use in conjunction withthe grasper 110. Each of FIGS. 41 and 43-51 show a cross-section throughthe instrument jaws as clamped on the tissue to be ablated. Eachelectrode is formed of a piece of electrically conductive metal that maybe plated with a biocompatible material.

With reference to FIGS. 41 and 42, the electrode geometry consists of alargely rectangular electrode with a window of material removed from thecentral region. The window area is filled with the insulator material122, 128. At the clamping surface the electrode insulator material leadsaway from the electrode on a radius. The electrode material protrudesoutside the clamping surface of the insulating material. However, theelectrode may also be flush with the clamping surface.

With reference to FIG. 43, the electrode geometry is largely rectangularand the electrode insulator material leads away from the electrode on aradius. The electrode is flush with the clamping surface of theinsulator material.

With reference to FIG. 44, the electrode is applied to fill a groove inthe insulator material by way of a plating process. The electrodegeometry is largely rectangular and the electrode insulator materialleads away from the electrode on a radius. The electrode plating islargely flush with the clamping surface of the insulator material.

With reference to FIG. 45, the electrode is formed into a U-shapedelement. The electrode insulator material leads away from the electrodeon a radius. As shown, the electrode material extends outside theclamping surface of the insulator material. However, the electrodematerial may also be flush with the insulator clamping surface.

With reference to FIG. 46, the electrode is applied to fill a groove inthe insulator material by way of a plating process, with the electrodegeometry being largely rectangular. The electrode insulator materialcreates a small flat surface perpendicular to the closure plane that islargely flush with the surface of the plate or electrode. As shown, theelectrode material is flush with the clamping surface of the insulatormaterial. However, the electrode material may also be applied so that itextends outside the insulator clamping surface.

With reference to FIG. 47, the electrode geometry is largely rectangularand the electrode insulator material leads away from the electrode on aradius. The electrode material extends outside the clamping surface ofthe insulator material.

With reference to FIG. 48, the electrode configuration is again largelyrectangular, with the electrode insulator material creating a small flatsurface perpendicular to the closure plane that is largely flush withthe surface of the plate or electrode. The electrode is flush with theclamping surface of the insulator material and a temperature sensingmeans, such as a thermocouple 166 (see also FIGS. 35 and 39), ispositioned in close proximity to the electrode, but electricallyisolated from the RF energy.

With reference to FIG. 49, the electrode is applied to fill a groove inthe insulator material by way of a plating process. The electrodegeometry is largely rectangular and the electrode insulator materialleads away from the electrode on a radius.

With reference to FIG. 50, the electrode is applied to the surface ofthe electrode insulator material by way of a plating process. Theelectrode geometry is largely rectangular with the electrode insulatormaterial leading away from the electrode on a radius. The electrodeplating is largely flush with the clamping surface of the insulatormaterial. With reference to FIG. 51, the electrode is round wire madefrom an electrically conductive metal that may be plated with abiocompatible material. The electrode insulator material leads away fromthe electrode on a radius. AS shown, the electrode material extendsoutside the clamping surface of the insulator material. However, theelectrode material may also be flush with the insulator clampingsurface.

A further embodiment of a grasper according to the present invention isshown in FIGS. 63-65 and is designated generally 250. The grasper 250has jaws 252, 254 similar in structure to those described above inconnection with the embodiments of FIGS. 28-32 and 33-40, but includes adifferent actuation mechanism. Specifically, the jaws 252, 254 of thegrasper 250 are biased so that they are normally in the closed position,the jaws being moved to the open position by moving the two handlemembers 256, 258 towards each other. This action serves to withdraw apush-rod 260 (FIG. 64), which is pivotally connected to the handlemembers 256, 258 by links 262, 264. With reference to FIG. 65A and FIG.65B. The distal end of the push rod 260 includes two pins 266, 268 whichare captured in slots 270, 272 in their respective jaw members 252, 254.When the pins 266, 268 are located in the distal ends of the slots 270,272, the jaws are in the closed position. The jaws 252, 254 open as thepins 266, 268 move proximally in the slots 270, 272 through thewithdrawal of the push rod 260 by the closing of the handle members 256,258.

The jaws 252, 254 also include a lost motion connection including aspring to bias the jaws toward the closed position. With reference againto FIG. 65A and FIG. 65B, the jaws 252 and 254 are pivotally connectedto each other by means of a pin 274. The pin 274 is secured to the jawmember 254, but is received in an elongated slot 276 in jaw member 252.The pin 274 is biased to the top of the slot 276, thus biasing the jaws252, 254 to the closed position, by means of a leaf spring 278 havingone end secured to the pin 274 and the other end captured between twostuds 280, 282 carried on the jaw member 252.

FIGS. 52A-K illustrate a series of 11 different lesions or ablationsthat may be made using either an open or a minimally invasive techniquewith the graspers described above. Turning first to FIG. 52A, there isseen a view of the heart showing the right and left atriums (as viewedfrom behind). The heart includes the left atrial appendage (LAA) and theright atrial appendage (RAA). The right pulmonary veins (RPVs) and leftpulmonary veins (LPVs) enter into the top of the left atrium. Thesuperior vena cava (SVC) and inferior vena cava (IVC) are also shown.The mitral valve annulus is designated as MVA, while the tricuspid valveannulus designated TVA. In FIG. 52A, 11 different lesions are indicatedby the reference numerals 1-11. A method for making each of theselesions is illustrated in the following FIGS. 52B-K. It should beappreciated that, depending upon a particular patient's indications, thelesions 1-11 may be created in a variety of combinations.

With reference to FIG. 52B, a method for making lesion 1 to circumscribethe right pulmonary veins (RPVs) is shown. This lesion is madecompletely epicardially in a manner similar to that illustrated in FIGS.23-27. FIG. 52C illustrates lesion 2, an epicardial ablation that fullycircumscribes the left pulmonary veins (LPVs). Again, this lesion may bemade in a manner similar to that illustrated in FIGS. 23-27.

FIG. 52D illustrates a method for making lesion 3, which connectslesions 1 and 2. Lesion 3 is made with only one of the jaws of thegraspers being located epicardially. The mating jaw is inserted into theinterior of the heart through a small incision which is sealed using apurse-string suture. The incision as illustrated is made interior thelesion 1 encircling the right pulmonary veins (RPVs).

In order to be sure that lesions 1 and 2 are fully transmural andcompletely encircle the RPV's and LPV's so as to effectivelyelectrically isolate the RPVs and LPVs from the atrium, one of the jawmembers of the grasper may be provided with an EKG sensor intermediatethe ends of the jaw. The EKG sensor is located on the jaw so that, whenthe grasper jaws are closed on the tissue intended to be ablated, theEKG sensor contacts the tissue outside of the ablation line on thepulmonary vein side of the line of ablation. Thus, by monitoring the EKGof the atrial tissue adjacent the pulmonary vein, the surgeon candetermine simultaneously with the creation of the ablation line whetherthe pulmonary veins have been electrically isolated from the atrium.

In addition, the grasper jaw may include pacing electrodes intermediateits ends. The pacing electrodes are located on the opposite side of theablation electrode from the EKG sensor, again outside the line ofablation. Thus, a pacing pulse can be transmitted by the pacingelectrodes which will be sensed by the EKG sensors when the jaws of thegrasper are closed on the tissue. The pacing and sensing continues asthe ablation electrodes are activated to create the lesion. When thelesion is complete, the EKG sensors will no longer be able to detect thepacing signal.

When a pacing electrode is paired with the EKG sensor, the EKG sensorsmay be on either side of the jaw, i.e., on either the pulmonary veinside or the atrial side of the ablation line created by the ablationelectrodes. The EKG electrodes and pacing electrodes are best seen inFIG. 66, where there is seen a pair of bipolar pacing electrodes 172 anda pair of bipolar EKG electrodes or sensors 174. The pacing electrodes172 and the EKG electrodes 174 are connected to a pulse generator andmonitor, respectively, in the well-known manner.

Lesion 4 connects the lesion 1, which surrounds the right pulmonaryveins, to the mitral valve annulus (MVA). It may be made through thesame incision and purse-string suture used for making lesion 3. Withreference again to FIG. 52D, the jaws of the grasper are merely rotateddown so that the distal end of the jaw overlies the mitral valveannulus.

When making lesion 4, care must be exercised in locating the grasperjaws so that the electrodes, when RF energy is applied, do not damagethe mitral valve leaflets. It is known that the electrical signalsgenerated by atrial tissue differ from the electrical signals generatedby ventricular tissue. Consequently, the distal tip of one of the jawmembers of the grasper includes an EKG sensor so that the EKG of thetissue contacted by the tip of the grasper can be monitored.

As best seen in FIGS. 66 and 67, the distal tip of the fixed jaw 116includes a pair of laterally-opposed bipolar EKG electrodes or sensors168 spaced slightly distally from the distal-most end of the electrode120. The sensors 168 are connected to conductive leads 170 (FIG. 33)that are adapted to be connected to an EKG monitor (not shown) toprovide a display of the EKG. Thus, as the jaws of the grasper arerotated downwardly after making lesion 3, the surgeon can constantlymonitor the EKG, looking for the change from an atrial EKG to aventricular EKG, to facilitate accurate placement of the jaw tip on themitral valve annulus, and away from the mitral valve leaflets.

It may also be desirable to make a lesion between the superior vena cava(SVC) and the inferior (IVC). This may be created in two steps, in whichlesions 5 and 6 are made. With reference to FIG. 52E, an incision withpurse-string suture is made approximately midway between the SVC andIVC, with one of the jaws of the grasper being inserted into theincision so as to have its end adjacent the base of the SVC. The lesion5 is formed and then the instrument is rotated 180° as shown in FIG.52F, to make lesion 6. Lesion 7 may conveniently be made through thesame incision and purse-string suture as lesions 5 and 6, as shown inFIG. 52G. Lesion 7 extends from between the SVC and IVC out toward theright atrial appendage (RAA).

A lesion 8 is made between the right atrial appendage and the tricuspidvalve annulus (TVA) utilizing an incision and purse-string suture madein the RAA, as illustrated in FIG. 52H. Lesion 8 is made on the oppositeside of the right atrium as lesion 7, and thus is shown in dotted linein FIG. 52A. A lesion 9 may also be made circumscribing the right atrialappendage so as to intersect both lesions 7 and 8. As shown in FIG. 52I,lesion 9 is made epicardially. A similar epicardial ablationcircumscribing the left atrial appendage is designated 10 andillustrated in FIG. 52J.

A final lesion 11 is illustrated that connects lesion 10 circumscribingthe left atrial appendage with lesion 2 that circumscribes the leftpulmonary veins. As illustrated, the lesion 11 is made utilizing anincision and purse string suture through which the grasper jaw isintroduced, the incision being located in the left atrial appendagebeyond the lesion 10.

In a further embodiment, the present device consists of two long,linear, wire-type electrodes, which are in parallel relationship to eachother, each approximately 1 mm in diameter, and 50 mm long. Theelectrodes are insulated along their entire surface with a thin layer ofhigh dielectric material such as polyamide, except for a thin strip ofelectrically conductive material that runs along the length of eachelectrode, in face-to-face relationship with each other. The electrodesare comprised of a high modulus material, such as tungsten or carbonfiber.

One of the electrodes is designed to be introduced into the interior ofa hollow organ through a small puncture wound in the wall of the organ.The second electrode is introduced on the opposite side of the holloworgan wall. The device incorporates a mechanism for advancing eachelectrode individually, or both simultaneously, in parallel relationwith each other. The device also includes a clamping mechanism thatbrings the two electrodes together so that their exposed conductivesurfaces are in face-to-face relation and the electrodes exertsufficient pressure to clamp the tissue. Once both electrodes have beenadvanced to their desired positions, the clamping mechanism is activatedwhich brings the two wires together, and clamps the tissue between thetwo exposed electrode surfaces. RF energy is then applied between thetwo electrodes, and the tissue is ablated in a long, continuous,transmural line. A monitoring device measures the voltage, current,impedance, and/or temperature between the two electrodes, and analgorithm determines whether the tissue is fully ablated.

This device provides a way to achieve and verify a fully transmural andcontinuous line of tissue ablation by locating the atrial tissue betweentwo bipolar wire electrodes, and clamping the tissue. The forcepsconsist of two electrode pads of opposite polarity designed to grasp andclamp tissue. A well-known method of determining the status of thetissue between the electrode pads is to monitor the current, voltage,and impedance of the tissue, as done using the Richard Wolf generatorfor bipolar forceps. It is well known in the art that the ablativestatus of tissue clamped between two bipolar electrodes can easily bedetermined by monitoring the increase in tissue impedance as the tissuedesiccates.

This device is to be used with an RF generator that monitors current,voltage, and impedance to determine the state of tissue ablation of thetissue compressed between the inner and outer electrodes. The RFgenerator will be equipped with an indicator which informs the user ofthe status of the clamped tissue, and when ablation is complete (i.e.,transmural along the entire length of the electrodes).

This device provides the capability of creating long, transmural lesionsthrough atrial wall tissue of varying thickness because it employs anactive bipolar electrode on each side of the atrial wall, and theablation proceeds from both the inside and outside of the atrial wall.The device is also unique in that the electrodes are used to compressthe tissue to be ablated. This compression is critical because theinside and outside surfaces of the atrium can have irregularities, and ahigh clamping pressure insures that both electrodes are making goodcontact with tissue along the full length of each electrode. Clampingthe tissue also reduces the distance between the electrodes, and makesthe ablation more efficient because the electrical energy is moreconcentrated. Because of this higher concentration of energy, lowerpowers and temperatures can be used to achieve complete ablation, andthe process is considerably faster.

As an example, to fully ablate a 5 mm deep lesion, 30 cm long can takeseveral minutes with an endocardial catheter electrode array, and thetemperatures can be as high as 80 to 90 degrees centigrade at the tissuesurface with the generator power as high as 40 to 50 watts. In benchtoptesting of the present invention in animal hearts, a fully transmural 30mm line through 5 mm of tissue was achieved in 5 seconds at 20 watts.

With reference to FIGS. 53-54, a further embodiment of the device isshown. The device consists of an inner wire electrode wire electrode201, an outer wire electrode 202, an inner slider button 203, an outerslider button 204, and a clamping slider tube 205 and button 206. Thedevice body 207 houses the wire electrodes, slider tube and buttons,connector wires 207 a and 208, and bipolar connector 209. The device mayalso include slit needle introducer tip 210.

The operation of the device begins by advancing the inner electrode wire201 by advancing the slider button 203. Once the inner electrode 201 isadvanced to the desired length, the outer electrode 202 is advanced byadvancing slider button 204. Note that further advancement of sliderbutton 204 also advances slider button 203, so that both electrodes 201and 202 advance simultaneously. Because of the bend 202 a in theelectrode wire 202, and the notch 205 a in the slider tube assembly 205,the slider tube advances along with the outer electrode 202. Once bothelectrodes are advanced to the desired length, the slider tube 205 isadvanced so that the end 205 b of the slider tube 205 contacts thearcuate wire segment 202 b of electrode wire 202. Further advancement ofslider tube 205 acts to compress the electrode wires 201 and 202together along the entire effective length L.

FIGS. 55 and 56 show two types of electrode wires, a piercing tip (FIG.56), and an obturator, or blunt tip (FIG. 55). The electrodes may besimilar in construction to those shown in FIGS. 2-6, which are describedabove. FIG. 57 shows a side view of the instrument tip.

FIG. 58A shows the instrument used to penetrate the wall of a holloworgan, such as the heart. The slit needle 210 penetrates tissue throughthe wall of the atrium 218. In FIG. 58B, the inner wire electrode 201 isadvanced through the puncture wound into the interior of the atrium. InFIG. 58C, the outer needle 202 is initially advanced onto the externalsurface of the atrial wall 218. FIG. 58D shows the inner 201 and outer202 needles as they are simultaneously advanced along the inner andouter surfaces of the atrial wall 218. FIG. 58E shows the pusher tube205 advanced to compress the tissue of the atrial wall 218 at location219. RF energy is then applied between the conductive strips 212 on eachelectrode to ablate the compressed tissue 219. FIG. 58F shows sectionB—B of FIG. 58E, with the inner 201 and outer 202 electrodes compressingthe tissue 219. The area of ablated tissue is shown as 220. Thealternate electrode configuration of FIG. 5 is shown in FIG. 58G. Bloodcells are represented as 221.

The compression of the tissue is important because it insures that theexposed electrode surface is not in contact with any tissue or bloodexcept the clamped tissue to be ablated. Referring to FIGS. 58F and 58Gone can see that the clamping of the tissue between the electrodesinsures that only the conductive area is in contact with the clampedtissue. Especially important is avoiding any contact between theconductive area of the electrode and blood in the atrium. Contactbetween an active electrode and blood in the atrium is major cause ofthrombus formation in ablation procedures. The compressed tissue acts toisolate the electrically active surface, and prevents inadvertent energydelivery to other parts of the heart or blood. The outside temperatureof the electrode can easily be monitored to insure that the temperatureof the insulation in contact with blood remains below a criticaltemperature (40° C., for example).

FIG. 59 shows a potential series of continuous transmural ablation lines222 located around the pulmonary veins 223 in the left atrium 224. Aseries of puncture wounds 225 are shown as one means to achieve thepattern of ablation lines (shown in dot-dash lines).

FIG. 60A shows a method for achieving a circumferential lesion in apulmonary vein 223. The inner needle 201 is a piercing tip as shown inFIG. 56. The needle is advanced completely through the wall of thepulmonary vein until it exits the vein. In FIG. 60B, the outer electrode2 is advanced parallel to the inner electrode 201. In FIG. 60C, theelectrodes are compressed, and the compressed vein wall tissue 226 isablated by applying RF energy between the two electrodes. In FIG. 60D,the electrodes are released, and the vein wall tissue 226 returns to itsoriginal shape. FIG. 60E shows the outer electrode 202 retracted backinto the instrument body, and the instrument is rotated 180 degreesabout the axis of electrode 201.

FIG. 60F shows the outer electrode 202 advanced along the opposite sideof the pulmonary vein from the ablated tissue 220. In FIG. 60G, theelectrodes are compressed, and the compressed vein wall tissue 227 isablated by applying RF energy between the electrodes. FIG. 60H shows theposition of the electrodes with the pusher tube retracted, and the fullycircumferential lesion 220. FIG. 60I shows the instrument retracted fromthe vein, and the circumferential lesion of ablated tissue 220.

FIGS. 61A-61J show the instrument used in a method to create acircumferential lesion around a pair of pulmonary veins 226 and 227. InFIG. 61A the inner electrode 201 is advanced into the side of the atrialwall 218, just below the ostium of the pulmonary vein 226 by advancingslider button 203. FIG. 61B shows electrode 201 and slider 203 fullyadvanced, and exiting the atrial tissue 218 just below the ostium ofpulmonary vein 227. FIG. 61C shows outer electrode 202 advanced fully inparallel and to the same length as inner electrode 201 by advancingslider 204. Note that slider tube button 205 has advanced to itsintermediate position.

FIG. 61D shows slider button 205 fully advanced, which clamps electrodes201 and 202 together just below the ostia of the pulmonary veins on theside of the veins indicated by tissue surface 218 a, and compresses theatrial wall tissue. RF energy is then applied between the twoelectrodes, and the clamped tissue 219 is ablated. In FIG. 61E,electrode 202 is retracted by retracting slider button 4. The line ofablated tissue is shown as 219 a. This line of ablated tissue 219 a willbe completely continuous and transmural, and connect inner needle entrypoint 229 with inner needle exit point 230 and extend along the side ofthe atrial wall.

FIG. 61F shows the device body 207 rotated 180 degrees about the axis ofthe inner electrode 201 so that the atrial surface 218 b on the oppositeside of the pulmonary veins is exposed. FIG. 61G shows slider button 204and outer electrode 202 advanced over the opposite surface of the atrium218 b. FIG. 61H shows slider button 205 advanced, and the electrodes 201and 202 clamping the tissue 219 b just below the ostia of the pulmonaryveins 226 and 227 along atrial wall 218 b. RF energy is then appliedbetween the electrodes 201 and 202 to ablate the compressed tissue 219b. In FIG. 61I the slider button 205 is retracted, and the electrodesrelease the tissue 219 b. The outer electrode is then retracted,exposing the tissue 219 b that is now fully ablated as indicated by theline 219 b. FIG. 16J shows a top view of FIG. 61I showing the continuousline of ablated tissue surrounding pulmonary veins 226 and 227,connected by entry point 229 and exit point 230 of internal electrode201. The electrode is then retracted, leaving a continuous transmurallesion that electrically isolates the pulmonary veins from the rest ofthe atrial tissue.

In another embodiment of the invention, a penetratingcompressive/tensile electrode is used. Once the jaws are positionedbelow the ostia of the pulmonary veins, the tissue is partially clamped,allowing continued flow from the pulmonary veins to the left atrium. Anelectrode needle is introduced which enters the left side of the atrialtissue and exits on the right side into a tip securing point on thelower jaw. This point will prevent the tip from moving axially when aneedle is pushed. The lower atrial tissue can be compressed by “pushing”on the needle with a force that compresses tissue between the needleelectrode and the lower jaw electrode. Bipolar RF energy is then appliedbetween the needle and lower jaw electrodes to ablate a line of tissuefrom the needle entry to exit point. Once the lower atrial tissue hasbeen ablated, the upper jaw is moved down to contact the tip of thelower jaw. Note that this still provides an open lumen for blood flowfrom the pulmonary veins to the left atrium. The needle is rotated 180degrees on its axis so that the electrode surface faces up. The needleis then “pulled” to create tension, and exert a compressive force thatcompresses tissue between the needle electrode and the upper jaw.Bipolar RF energy is then applied between the needle electrode and upperjaw to ablate the tissue. Note that the partial closing of the upper jawto contact the tip of the lower jaw could be done prior to compressingthe lower atrial tissue.

With reference to FIGS. 62A-62I the clamping apparatus as generallydescribed above is shown. As illustrated, the device is a “pliers type”apparatus. The device is shown clamped around the atrial tissue belowthe ostia of the pulmonary veins. In FIGS. 62B-62D, an electrode needleis advanced through the atrial tissue to contact a receiver at the tipof the device. FIG. 62E shows one method of clamping the tissue to arigid needle electrode, using a non-rigid outer clamping member thatflexes either by further motion of the handle as shown or by furtherextension of the electrode member. FIG. 62F shows both sides of theclamping member flexed, and the tissue compressed between. FIG. 62Gshows the position of the clamping members and electrode prior to tissueclamping. FIG. 62H shows these positions during tissue clamping. BipolarRF energy is applied between the clamping members, and the innerelectrode to ablate the atrial tissue, creating a lesion, as shown inFIG. 62H. Note also, that if the inner electrode had only one exposedelectrode surface, the tissue ablation could be carried out first on oneside, then the other, without occluding the lumen between the pulmonaryveins and the atrium.

FIG. 62I shows another way to achieve tissue compression by advancing arelatively flexible needle electrode which bends as shown to compressthe tissue between the electrode and one of the device jaws.

A further aspect of this invention provides three methods which may beused to gain access to ablate cardiac tissue. The first method gainsaccess to the heart by opening the patient's chest or thoracic region.The second method gains access to the heart by intercostal incisionswhereby access to the heart is achieve between the ribs. Finally, thethird method utilizes a sub-xyphoid approach. In any event, each methodis adapted to place the ablations at previously identified locationsthat require ablation.

The first method is illustrated in FIGS. 68-77. Access to the patient'sheart is achieved by opening the patient's chest. FIGS. 68-77 show apatient's rib cage R, sternum ST, xyphoid XP, coastal cartilage C, rightlung RL and left lung LL. This method requires a gross thoracotomy suchas where the ribs or sternum are cut in half with an anterior incisionor removal of a portion of the ribs or sternum such as in the form of amedian sternotomy. Percutaneous penetration is made by an initialincision into the patient's chest above the sternum. In FIG. 68,percutaneous penetration is made in the longitudinal direction along thepatient's sternum along line 300. Thereafter, the sternum is cutlongitudinally and each side of the sternum pushed apart so as to gainaccess to the patient's thoracic or chest cavity 302, as shown in FIGS.69 and 73. Spreading of the sternum and ribs is achieved using a wellknown spreading device or the like. If the lungs are not deflated thenthey will need to be moved aside using clamps 304 or the like to gainaccess to the heart. Once access to the heart is cleared, all ablationlocations must be located and identified.

Locating and identifying the ablation locations may be performed by oneof several different instruments such as a bullet dissector 306, whichis best shown in FIGS. 70 and 71. The bullet dissector 306 identifies alocation which requires ablation and creates a viewing and working spacefrom which to ablate the location. The bullet dissector includes abullet or head 308 and a body 310. The head 308 is made of a clear ortransparent material and has a plurality of irrigation holes 312. Thebody 310 includes a tube 314 which supplies saline to the head 308. Assaline is supplied through the tube 314 to the head 308, it flows out ofthe irrigation holes 312, as indicated by the arrows in FIG. 70. Thebody 310 of the bullet dissector may be attached to an endoscope 316 orother suitable device, which includes a light or fiberoptic cable 318 toilluminate the site being dissected. The size of the endoscope to whichthe bullet dissector is attached may vary although the preferreddiameter range is between 2 mm to 10 mm. The diameter of the endoscopeis approximately equal to or smaller than the diameter of the dissectorhead. The endoscope is preferably connected to the rear of the dissectorhead. A portion of the endoscope cable 318 may be inserted into thedissector head 308 while maintaining seal around the cable so thatsaline flow is unaffected. The endoscope may include a viewing lens orcamera which is connected to a video monitor which displays the locationwhich is viewed.

The continuous flow of saline from the bullet dissector 306 allows thesaline to flush blood and other body debris from the transparent head308 and endoscope viewing lens so as to provide a clear viewing space.As saline flows out of the head, the flow of saline pushes against theadjacent tissue and aids in dissection by, for example, separating thepericardium from the heart. The continuous flow of saline creates aworking space between the dissector and the surrounding tissue andensures that this space is positively pressurized.

In addition, the head 308 of the bullet dissector also may be designedto allow easy dissection around the pulmonary veins or other cardiactissues. The head 308 is bullet shaped. It has a rounded distal tip 309which gently separates or dissects tissue. The diameter of the head 307may be equal to or larger than the body 310.

Once the thoracic cavity is accessible, the bullet dissector 306 isinserted into the patient's chest cavity adjacent the heart, as shown inFIG. 72. The bullet dissector 306 may locate the ablation locations overa pericardium P. Alternatively, the pericardium may be pierced so as tocontact an epicardium E so as to allow the bullet dissector to directlycontact the surface of the heart. The bullet dissector assists theidentification and location of ablation locations. Saline exits theirrigation holes 312 of the bullet dissector 306 and insufflates theintrapericardial space around the ablation location. Insufflating theablation location with saline creates a viewing and working space withinthe intrapericardial space 318 by which the ablation location may beaccessed. Saline also clears blood away from the ablation location andcreates a positive pressure in the working space. A positive pressuremay be particularly helpful in eliminating the need for complicatedhemostatic devices or valves, and/or avoiding or limiting the need toseal off the pericardial incision by a valve, balloon or other inflationdevice. Insufflating can be done with any compatible biological fluid:saline, contrast medium, CO2, or blood. However, saline or CO2 ispreferred because these provide clarity with which to view the space andidentify the area to ablate. Excess saline may exit the intrapericardialspace and can be removed by a drainage tube which can be inserted intothe chest cavity.

After the ablation locations are located and identified, the ablation orclamping device is then introduced into the patient's chest andpositioned in contact with the location. The ablation device which isgenerally used for the open heart procedure is the grasper shown anddescribed in FIGS. 28-32 although use of other graspers or devices isalso contemplated. The ablation device also may have a shape which isparticularly suited to the ablation location to be contacted. Duringinsertion of the ablation device, the bullet dissector preferablyremains inserted so as to maintain the positively pressurized workingspace and to assist in visualizing the ablation device. Thereafter, thelocation is ablated using an RF energy ablation technique as disclosedherein.

In FIG. 73 cardiac tissue is ablated from both the right and left sides.FIG. 73 shows ablation of the left atrium in the region of the right andleft pulmonary veins, RPV and LPV, respectively. The right pulmonaryveins RPV are ablated using a grasper 319 such as the one shown anddescribed in FIGS. 28-32. The left pulmonary veins LPV are ablated usinga similar grasper 321 which is rotated 180 degrees. Jaw members of eachgrasper 319, 321 may be curved and oriented such that the concaveportion of the jaw members face the pulmonary veins and the convexportion of the jaw member face away. This orientation is preferred toprovide effective clamping and ablation of the atrium near the pulmonaryveins. Because the patient's chest is open, the graspers may be in theform of open scissors such as, for example, the grasper shown in FIGS.28-32, or an ablation device with sliding jaws generally illustrated inFIGS. 1-27 or of the type shown in FIGS. 33-37. It is contemplated thatdifferent ablation devices may be used to effectively ablate differentcardiac tissues.

FIG. 74 shows eleven different locations that may be ablated in treatingatrial fibrillation according to any of the methods described herein. Byway of example, FIGS. 75-76 show ablation of an epicardial surfaceadjacent the left and right pulmonary veins, LPV and RPV, respectively.In FIGS. 74-77, the referenced portions of the heart include the rightatrial appendage RAA, left atrial appendage LAA, left atrium, superiorvena cava SVC, inferior vena cava IVC.

FIG. 77 shows bilateral ablation near a pair of pulmonary veins 320 bycreating an ablation lesion 322 on the left atrium 324. Bilateralablation creates a circumferential ablation lesion on the atrium whichisolates the pair of pulmonary veins.

FIGS. 78-86 illustrate the second method which achieves access to theheart using a percutaneous intercostal penetration with like partsreferenced with like letters and numbers. This method is less invasivethan a gross thoracotomy. In FIG. 78, one or more percutaneousintercostal penetrations may be made in one or more access locations336, 338 between the ribs. The direction and location of thepercutaneous intercostal penetrations will depend on where the cardiactissue to be treated is located, so that ablation of the cardiac tissueis accessible by an appropriate ablation device. For example, entrythrough access locations 336 is helpful in achieving access to ablationlocations located on the right side of the heart and, likewise, accesslocations 337 achieve access to the left side of the heart. For most, ifnot all, intercostal penetrations the lung may be temporarily deflatedto allow easier passage of the instrument through the pleural space PS,although such deflation may not be absolutely necessary. One or moresuitable access devices may be used to obtain access to the intercostalspaces between the ribs. These devices may be used to protect theincision location and minimize trauma thereto and may include, but arenot limited, to trocar sleeves, ports, or other types of percutaneousaccess cannulae. By way of example, not limitation, FIGS. 79-86 shows asupporting ring 338 with tensioning members 340.

Once the intercostal penetration is made, the bullet dissector isintroduced through the incision, as shown in FIG. 79. Turning to FIG.80, the pericardium P is preferably pierced or punctured so as to allowthe head 308 of the bullet dissector 306 into an intrapericardial space342. FIGS. 81-83 illustrate intercostal ablation where the right lung RLis deflated and the left lung LL remains inflated. As a result, thebullet dissector traverses the pleural space PS on its path to theheart. The bullet dissector insufflates the intrapericardial space 342with saline and creates a clear working space which is positivelypressurized in relation to the pressure outside the pericardium. Thedissector is preferably attached to an endoscope or like device whichallows for viewing of the ablation location and is inserted into theintrapericardial space 342 until an ablation location is located. Thenthe ablation device 344 is inserted into the incision and advanced tothe ablation location.

FIG. 83 shows the ablation device 344 ablating cardiac tissue adjacentthe right pulmonary veins RPV. By way of example but not limitation, theablation device for the intercostal and sub-xyphoid methods may be thegraspers shown and described herein in FIGS. 33-37 or FIGS. 63-65.Different ablation devices may be used for reaching different areas ofcardiac tissue. The ablation devices may have different curvatures forreaching certain portions of the heart. For example, an ablation devicefor the left atrium adjacent the left pulmonary veins may have adifferent curvature than the ablation device for the right atriumadjacent the right pulmonary veins. FIGS. 83A and 83B show right andleft curved graspers 350 and 352, respectively, which are similar to thegrasper in FIGS. 33-37 except that the graspers in FIGS. 83A and 83Bhave right and left curved jaw members 354 and 356, respectively. Boththe right and left curved graspers 350 are helpful in ablating cardiactissue adjacent the right and left pulmonary veins depending on whatdirection of approaches are used. Likewise, the left curved grasper 352assists in ablating cardiac tissue adjacent the left pulmonary veins.Other shapes of ablation devices will be apparent to those skilled inthe art. It is noted that the intercostal and sub-xyphoid methodspreferably will utilize ablation devices having a long handle such thatwhen the instrument reaches the ablation location a gripping portion ofthe device remains outside the entry location into the patient forcontrol by the doctor.

Using the intercostal method, transmural ablations may be performed onother cardiac tissue using RF energy, as previously described herein.Ablation is repeated until all ablation locations have been treated.Ablation devices may be inserted into different access locations 336depending on which directional approach is preferred for the cardiactissue which requires ablation. Different ablation devices may beinserted depending on which cardiac tissue requires treatment. Once allareas are treated on the right side in FIG. 83 with the appropriateablation device, the right lung is re-inflated and the access location336 is closed. The method is repeated for the left side if necessarythrough access location 337. FIG. 84 shows ablation of cardiac tissueadjacent the left pulmonary veins LPV.

FIGS. 85 and 86 show intercostal ablation which occurs while both lungsare inflated. It may be necessary to use clamps 346 or the like to pullportions of the lung away from the heart and provide a pathway foradvancing the bullet dissector 306 and the ablation device 344. Whileboth lungs remain inflated, it is possible that cardiac tissue may betreated from both sides of the chest, at the same time, with onedissector 306 and one ablation device 344 within the access location 336and another dissector and ablation device within the access location337.

In the sub-xyphoid method, the initial incision is made beneath the ribcage R, preferably between the xyphoid XP and the adjacent costalcartilage C. In FIGS. 87-91, like parts are again shown with like letterand number. FIG. 87 shows access locations 358 for the incision. InFIGS. 88-91, the ablation device 360 is advanced through thepercutaneous sub-xyphoid penetration to the aberrant cardiac tissuewhich requires ablation. In FIGS. 88-90, the bullet dissector 306 maythen be inserted through a percutaneous intercostal penetration 362 toidentify the ablation location and assist in guiding the ablationdevice. Insufflation from the dissector 306 creates the positivelypressurized and clear working space. Thus, the cardiac tissue may beeasy located and ablated with the ablation device 360, as shown in FIGS.89 and 90.

Using the sub-xyphoid approach, it also may be possible to performablation on both pairs of pulmonary veins at the same time eitherthrough the same incision or through separate incisions. FIG. 91 showsablation of the left atrium near the right and left pulmonary veins.Right and left curved ablation devices 350 and 352 are similar to thosedescribed herein in FIGS. 83A and 83B. The ablation devices are insertedthrough access locations 358, although it is also possible that bothdevices could be inserted through one access location 358. Correspondingbullet dissectors 306 may be inserted through percutaneous intercostalpenetrations 362 on the right and left sides, or the bullet dissectorsmay be inserted through a sub-xyphoid access location 358.

In FIGS. 92 and 93, the bullet dissector and ablation device are bothinserted using a sub-xyphoid approach. The bullet dissector and ablationdevice may be separate as previously described or they may be combinedinto a single instrument for this, as well as the prior methods. FIGS.92 and 93 show ablation by a combined dissector and ablation instrument364. In FIG. 94, the combined instrument 364 includes a proximal end 366which includes a bullet dissector head 368 and an endoscope 370. Theproximal end 366 is carried by or mounted to an ablation device.Although the ablation device which is shown is similar to the graspershown in FIGS. 63-65, other devices are possible. The ablation deviceincludes grasping jaws 372, an elongated handle 374 and handle members376. A saline irrigation tube 378 is carried by the handle 374 andsupplies saline to the bullet dissector head 368. The combineddissector-ablation instrument 364 may be used for any of the abovemethods. Use of the instrument 364 in the intercostal method isillustrated by way of example in FIG. 95.

FIGS. 96-101 illustrate using the sub-xyphoid approach where the bulletdissector and ablation device are separate instruments through a singleaccess location 380. An incision is first made in the sub-xyphoid regionat the access location 380 near the tip of the xyphoid, as illustrated.This access location 380 is preferred because it allows access to bothsides of the chest for treatment as needed. The size of the incision isabout 1 cm. Then the bullet dissector 306 is inserted through the accesslocation 380 and advanced to the pericardium P. The bullet dissector ispreferably attached to an endoscope as previously described to aid invisualization. Once the bullet dissector proceeds to the appropriatepoint on the pericardium, a suitable cutting instrument such as aendoscope knife or scissors is introduced alongside the bullet dissectorto create a small incision 382 in the pericardium just large enough forthe head of the bullet dissector. The bullet dissector 306 is theninserted into the intrapericardial space 342 and advanced through theintrapericardial space, dissecting the pericardium from the heart as itadvances, to the cardiac tissue to be treated.

For example, as shown in FIGS. 98-99 the bullet dissector 306 isadvanced within the intrapericardial space to the confluence of the leftatrium and the pair of left pulmonary veins LPV. It is expected thatminimal dissection of tissue will be performed by the bullet dissectoraround the left pulmonary veins whereas more tissue dissection will berequired around the right pulmonary veins RPV. During dissection thebullet dissector will be advanced both above and below the atrium, thepulmonary veins and the confluence where the pulmonary veins meet theatrium to provide a working space which, as described above, ispositively pressurized by insufflation. Creation of the working spaceallows for insertion of the jaws of the ablation device and aids invisualizing the cardiac tissue which requires treatment.

Once dissection is completed, an ablation device 384 may be insertedthrough the sub-xyphoid access location 380. The ablation device may beinserted into the intrapericardial space alongside the bullet dissector306 either by enlarging the pericardial incision using a suitablecutting device or by causing the pericardial incision to stretch orwiden to accommodate the ablation device. It is also possible to removethe bullet dissector 306 and then insert the ablation device, althoughuse of the bullet dissector in combination with the ablation device ispreferred. The ablation device is advanced to the cardiac tissue to betreated such as, for example, the confluence of the atrium and thepulmonary veins.

With the aid of the bullet dissector and endoscope, the tissue to betreated is identified. Within the working space created by the bulletdissector, one jaw of the ablation device is positioned below thepulmonary veins and the other jaw is positioned above the pulmonaryveins. The ablation device is properly positioned around the tissue tobe treated and then clamped. Verification may be performed to ensurethat the clamped tissue between the jaws of the ablation device is thelocation which requires ablation. The bullet dissector may helpvisualize and confirm that the appropriate cardiac tissue is beingtreated. The curved jaw members of the ablation device should beoriented such that the concave portion faces the pulmonary veins and theconvex portion faces the atrium.

Ablation of the cardiac tissue is performed by using RF energy to createan ablation lesion, as previously described. The sub-xyphoid approachmay be used to create ablations as shown in FIGS. 74-77. For example,FIG. 101 shows the ablation device ablating the left atrium near theleft pulmonary veins which creates a circumferential ablation lesionsimilar to the one shown in FIG. 77. Thereafter the jaws of the ablationdevice are unclamped and moved to another location which requiresablation.

The sub-xyphoid method can be repeated as necessary to create additionalablations. For example, a second circumferential ablation may be createdaround the right pulmonary veins. When using an ablation device similarto the grasper shown in FIGS. 63-65, ablation of a second pair ofpulmonary veins may be performed by rotating the grasper 180 degrees sothat the concave portion of the jaw members faces the pulmonary veins.In the case of the grasper in FIGS. 33-37, 83A and 83B, it may benecessary to use right and left curved ablation devices when using thesub-xyphoid approach so that the concave portion of the jaw membersfaces the appropriate pair of pulmonary veins. For example, the rightcurved grasper 350 may be used to treat the atrium near the rightpulmonary veins and then withdrawn through the sub-xyphoid accesslocation 380. Thereafter, the left curved grasper 352 may be insertedthrough the access location 380 and used to ablate the atrium near theleft pulmonary veins.

During ablation drainage of excess fluid may be performed by inserting adrainage tube through the sub-xyphoid access location 380. Once allablation locations are treated, the ablation device and bullet dissectorare withdrawn and the sub-xyphoid access location 380 is closed usingwell-known techniques. It is not necessary to suture the pericardiumincision.

Importantly, each method may be performed with a beating heart or withthe heart stopped. Where the heart is stopped, it is understood that thepatient must be connected to a cardio-bypass machine. The methods may beperformed either with the lungs inflated or deflated. If the lung isdeflated, then the patient must be connected to a respirator. It isrealized that where both the heart is stopped and the lung deflated,then the patient will be connected to a cardiopulmonary bypass system.Where the lung is deflated, it may be preferred to deflate only one lungat a time before proceeding to deflate the other lung. For example,where cardiac tissue adjacent each pair of right and left pulmonaryveins requires treatment, either the right lung or the left lung may bedeflated, but not both. After all cardiac tissue requiring ablation istreated on the deflated side, the lung is re-inflated and the process isrepeated for the other side of the heart.

Each method may be used to create transmural ablation as previouslydescribed herein for epicardial or endocardial surfaces. For epicardialablations, an incision is usually made into the pericardium to accessthe epicardial surface. Although it is possible to perform ablationswithout penetrating the pericardium, penetration into theintrapericardial space, the space within the pericardial cavity betweenthe pericardium and the epicardium, may allow for better positioning ofthe ablation device for ablation of the identified cardiac tissue. Wherethe ablation device is inserted into the intrapericardial space, it isadvanced to the location which has been identified as requiringablation. The ablation device directly contacts the epicardial surfaceof the heart relating to this location and the location is ablated.Methods of epicardial ablation for creating lesions around the pulmonaryveins are disclosed in U.S. Pat. No. 6,161,543, which is incorporatedherein by reference.

For endocardial ablation, an incision is made in the heart wall by ablade on the tip of the ablation device or by other suitable instrument.The incision in the heart wall may be treated with an appropriate suturesuch as a purse string suture 327 shown in FIG. 76. Then the dissectorand endoscope can locate and identify the location to be ablated. Oncethe location is identified, one of the jaws of the ablation device orgrasper is inserted into the heart to directly contact the endocardialsurface which requires ablation. After ablation, the jaw of the ablationdevice, is withdrawn back through the incision. The process is repeateduntil all locations are treated.

Thus, it can be seen that a transmural ablation device and method havebeen provided that overcome the limitations of the prior art. First,current technology involves ablation devices deliver ablation energy toeither the inside (endocardium) or outside (epicardium) of the heart.Using these techniques, the tissue ablation proceeds from one wall ofthe heart through the tissue to the opposite wall. To date, there hasbeen no reliable way to consistently achieve lesions that penetrate thefull thickness of the atrial wall (transmural lesions), and there hasbeen no way to determine either continuity or transmurality of theselesions. If the lesion does not penetrate through enough of the atrialwall, conduction can still occur, and the lesion does not fully blockthe electrical signals that are causing the arrhythmia. Using anendocardial approach, if the lesion penetrates too far through the wall,critical structures such as coronary arteries, veins, or the esophaguscan be damaged on the outside of the heart. Using an epicardialapproach, if the lesion penetrates too far, blood can be coagulated, orcritical structures such as valves, nodes, or connective tissue can bedamaged on the inside of the heart.

There has also been no reliable and consistent way to safely achievefully continuous, long (greater than 1 cm) lesions in the atrial wallwithout a high risk of thrombus, damage to critical structures, orextensive damage to the atrial tissue.

The present invention overcomes these shortcomings because theconductive area of each electrode is very narrow compared to the widthof the clamped area. As a result, the thermal damage to the tissue isminimal. In contrast, current technology uses catheter electrodes whichare typically 1 or 2 mm diameter requiring a lesion width of almost 8 mmto achieve a depth of 5 mm. Using the present invention, a lesion depthof 5 mm with a width of less than 2 mm can be achieved. This aspect ofthe invention allows for longer linear lesions with less power deliverybecause less tissue is being heated. There is, therefore, considerablyless damage to healthy atrial tissue for a lesion of a given depth andlength. Recent efforts in creating linear lesions using endocardialelectrodes resulted in ablation of over 20% of the atrial endocardium,and a commensurate decrease in atrial contractility.

Another advantage of this device is that ablation can be done on abeating heart. Using a high modulus material such as tungsten or carbonfiber would allow a minimum diameter, and a maximum clamping pressurefor a given clamping length. Once the device is clamped onto the atrialwall, the position of the electrodes can be verified by visuallyinspecting the position of the outer electrode before delivery of RFenergy. If the clamping pressure is higher than the atrial pressure,then clamping over a coronary artery would cut off blood flow, and theresulting change in the EKG would act as a warning to the user prior toapplying RF energy. The clamping will prevent any movement of theelectrodes relative to the heart wall, and RF energy can be applied withconfidence that the ablated tissue will be contained completely betweenthe two electrodes.

Another important feature of this device is that the energy transfer islimited to the tissue clamped between the two electrodes. The insulatedelectrodes protect structures on the outside of the heart from beingexposed to RF energy. Because of this limitation of current flow, damageto critical structures can be avoided.

Another advantage of this device is that it can easily be adapted to aminimally invasive thoracoscopic approach. The device shown has beenreduced to a 5 mm diameter device, and can probably be reduced to 3 mmor less. Using video thoracoscopy, the device could be introducedthrough a small intracostal incision, and used to create fullytransmural linear lesions on a beating heart, possibly under localanesthesia on an anesthetized patient.

Accordingly, a device and method for performing transmural ablation hasbeen provided that meets all the objects of the present invention. Whilethe invention has been described in terms of certain preferredembodiments, there is no intent to limit the invention to the same.Instead it is to be defined by the scope of the appended claims.

1. A device for clamping and ablating cardiac tissue to form transmurallesions therein, comprising: first and second jaws relatively movablebetween an open position to receive cardiac tissue therebetween and aclamped position compressing the cardiac tissue; a first elongatedelectrically conductive member carried on the first jaw and a secondelongated electrically conductive member carried on the second jaw; thejaws being generally parallel in a range of movement between the openand clamped positions; the first and second conductive members beingconnectable to an RF energy source to pass electrical current throughtissue clamped between the jaws; at least one of the jaws being biasedso as to urge the jaws toward the clamped position with a force thatincreases as the separation of the jaws increases; whereby cardiactissue may be clamped with a force that is proportional to the thicknessof the clamped tissue and that is generally uniformly applied by theparallel jaws.
 2. The device of claim 1 wherein at least one of the jawsis operable by a drive member having a proximal and a distal end, thedistal end supporting the one jaw and the proximal end being received ina carriage member slidably supported in a handle member, and a biasingspring being located interior of the carriage member.
 3. The device ofclaim 2 further comprising a movable member associated with the carriagemember for selectively varying the degree to which the spring iscompressed.
 4. The device of claim 2 wherein the carriage includes anexterior engagement surface and further comprising a latch pivotallysecured to the handle for selectively engaging the engagement surface,whereby the drive member is locked in position with respect to thehandle members.
 5. The device of claim 1 wherein each jaw has a facing,tissue-engaging non-conductive surface and the elongated conductivemember is generally centrally located relative to such surface.
 6. Thedevice of claim 5 wherein each tissue engaging surface has a generallycentrally located slot extending along the jaw.
 7. The device of claim 5in which each conductive member is at least partially disposed withinthe respective jaw and current flows through the slot to tissue clampedbetween the jaws.
 8. The device of claim 6 in which at least a portionof the conductive member extends through the slot to contact tissueclamped between the jaws.
 9. The device of claim 5 in which the tissueengaging surface and conductive member each have a width and the widthof the conductive member is less than or equal to ⅓ the width of the ofthe engaging surface.
 10. The device of claim 1 in which at least one ofthe conductive members defines an interior lumen.
 11. The device ofclaim 1 in which at least one of the conductive members is a wire. 12.The device of claim 1 in which at least one of the conductive membershas a convex tissue-engaging surface.
 13. The device of claim 6 in whichthe tissue engaging surface and slot each have a width and the width ofthe slot is less than or equal to ⅓ the width of the tissue engagingsurface.
 14. The device of claim 8 in which the portion of theconductive member extending through the slot and the tissue engagingsurface each has a width and the width of the conductive member portionis less than or equal to ⅓ the width of the tissue engaging surface. 15.The device of claim 1 in which the jaws are generally parallel in theopen position, in the clamped position and during movement between theopen and clamped positions.